1. Field of the Invention
The present invention relates to a transmission and reception multi-beamforming method using a multi-transmission antenna and a multi-reception antenna, and more particularly, to a transmission and reception multi-beamforming method based on a codebook.
2. Description of the Related Art
The present invention provides a transmission and reception multi-beamforming scheme using a multi-transmission antenna and a multi-reception antenna, and the transmission and reception multi-beamforming scheme based on a codebook.
The beamforming scheme may directionally transmit and receive, using a multi-antenna, a radio wave based on a spatial distribution of users and thus, may reduce interference and may increase a power efficiency and a quality of communication. The multi-antenna for beamforming may use a linear antenna array, a plane antenna array, and the like.
In the multi-antenna system, a beamforming apparatus may perform beamforming by applying weights appropriate for each transmission and reception antenna. Weighted signals, which are generated by multiplying signals and the weight, are added together and the beamforming may be performed using the added signals as an output signal.
A multi-antenna beamforming scheme may be applicable to each of a transmitting end and a receiving end, and weights for beamforming may be appropriately selected and used based on an environment and a location between the transmitting and receiving end.
A beamforming scheme based on a codebook may be a scheme that predetermines weighted-vectors for the beamforming and may select an optimal beamforming weighted-vector based on the transmission and reception environment to increase the quality of communication.
The weights used by a multi-beamforming apparatus may be classified, based on an antenna array, as a weighted-vector to be used for a one-dimensional array, such as the linear antenna array, and a weighted-matrix to be used for a two-dimensional array, such as the plane antenna array. The weighted-vector used for the two-dimensional array may be calculated based on the weighted-vector used for the one-dimensional array, as expressed by Equation 1.Wk,l=(wk)T·wl.  [Equation 1]
In Equation 1, wk may denote a kth weighed-vector and wl may denote a first weighed-vector. (g)T may denote a transposed matrix.
A spatial diversity processing apparatus may be applied to the receiving end to enhance a quality of a received signal. A complex channel gain between an ith transmission beam and a jth reception beam may be sequentially estimated with respect to N transmission beams, a complex channel gain or the estimated complex channel gain are multiplexed with a transmission beam weighted-matrix, and the multiplexed value is transmitted to the transmitting end and applied to the multi-beamforming apparatus. Lastly, a gain of the spatial diversity may be expressed by Equation 2.
                              G          div                =                              ∑                          i              =              1                        N                    ⁢                                    ∑                              j                =                1                            N                        ⁢                                                                                                  h                                          i                      ,                      j                                                                                        2                            .                                                          [                  Equation          ⁢                                          ⁢          2                ]            
In Equation 2, a channel is a single input single output (SISO), for each transmission beam, and hi,j may denote the complex channel gain between the ith transmission beam and the jth reception beam